bytedruid
Mongoose
Actually I wouldn't say it's all that rare. It was a central plot point of Star Trek 6 the Undiscovered Country anyway. Typically engineers design standard consumer items in a fail safe manner. For example if you take your hand off the yoke of a Cessna 172 it returns itself to level flight, etc. In this case the fail safe is to allow for acceleration, potentially away from something dangerous, even when the plating doesn't work.The inability of grav plates to fail catastrophically seems to be a pretty standard space opera trope. There are very few sci fi ships that are not built in this manner. Either the setting is rockets and tailsitters or the ships are built as if grav doesn't fail under acceleration.
Given this consideration, and the fact that form follows function, I'd presume the form of most non-atmospheric ships would be more like an office building then a steamship. For atmospheric craft, ease of access while planet-side could dictate other forms.
So to flip the question on it's head, why would you even want to put the primary acceleration vector parallel to the floor? What first-principles benefit is there to be gained from that?